<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>选择下拉列表的颜⾊后，点击按钮删除选中的列表颜⾊</title>
</head>

<body>
  <select id="colorSelect">
    <option>Red</option>
    <option>Green</option>
    <option>White</option>
    <option>Black</option>
  </select>
  <button onclick="del()">删除</button>
</body>
<script>
  function del() {
    var item = document.getElementById('colorSelect')
    var ii = item.selectedIndex  //被选定的选项的索引
    item.options.remove(ii)

  }
</script>

</html>